text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #define _USE_MATH_DEFINES // For VC++ to get M_PI. This has to be first.
  
  #include "ui/views/view.h"
  
  #include <algorithm>
  #include <cmath>
  #include <memory>
  #include <utility>
  
  #include "base/logging.h"
  #include "base/macros.h"
  #include "base/memory/ptr_util.h"
  #include "base/message_loop/message_loop.h"
  #include "base/stl_util.h"
  #include "base/strings/stringprintf.h"
  #include "base/strings/utf_string_conversions.h"
  #include "base/trace_event/trace_event.h"
  #include "build/build_config.h"
  #include "third_party/skia/include/core/SkRect.h"
  #include "ui/accessibility/ax_enums.h"
  #include "ui/base/cursor/cursor.h"
  #include "ui/base/dragdrop/drag_drop_types.h"
  #include "ui/base/ime/input_method.h"
  #include "ui/compositor/clip_recorder.h"
  #include "ui/compositor/compositor.h"
  #include "ui/compositor/dip_util.h"
  #include "ui/compositor/layer.h"
  #include "ui/compositor/layer_animator.h"
  #include "ui/compositor/paint_context.h"
  #include "ui/compositor/paint_recorder.h"
  #include "ui/compositor/transform_recorder.h"
  #include "ui/display/screen.h"
  #include "ui/events/event_target_iterator.h"
  #include "ui/gfx/canvas.h"
  #include "ui/gfx/geometry/point3_f.h"
  #include "ui/gfx/geometry/point_conversions.h"
  #include "ui/gfx/interpolated_transform.h"
  #include "ui/gfx/path.h"
  #include "ui/gfx/scoped_canvas.h"
  #include "ui/gfx/skia_util.h"
  #include "ui/gfx/transform.h"
  #include "ui/native_theme/native_theme.h"
  #include "ui/views/accessibility/native_view_accessibility.h"
  #include "ui/views/background.h"
  #include "ui/views/border.h"
  #include "ui/views/context_menu_controller.h"
  #include "ui/views/drag_controller.h"
  #include "ui/views/focus/view_storage.h"
  #include "ui/views/layout/layout_manager.h"
  #include "ui/views/views_delegate.h"
  #include "ui/views/widget/native_widget_private.h"
  #include "ui/views/widget/root_view.h"
  #include "ui/views/widget/tooltip_manager.h"
  #include "ui/views/widget/widget.h"
  
  #if defined(OS_WIN)
  #include "base/win/scoped_gdi_object.h"
  #include "ui/native_theme/native_theme_win.h"
  #endif
  
  namespace views {
  
  namespace {
  
  #if defined(OS_WIN)
  const bool kContextMenuOnMousePress = false;
  #else
  const bool kContextMenuOnMousePress = true;
  #endif
  
  // Default horizontal drag threshold in pixels.
  // Same as what gtk uses.
  const int kDefaultHorizontalDragThreshold = 8;
  
  // Default vertical drag threshold in pixels.
  // Same as what gtk uses.
  const int kDefaultVerticalDragThreshold = 8;
  
  // Returns the top view in |view|'s hierarchy.
  const View* GetHierarchyRoot(const View* view) {
    const View* root = view;
    while (root && root->parent())
      root = root->parent();
    return root;
  }
  
  }  // namespace
  
  // static
  const char View::kViewClassName[] = "View";
  
  ////////////////////////////////////////////////////////////////////////////////
  // View, public:
  
  // Creation and lifetime -------------------------------------------------------
  
  View::View()
      : owned_by_client_(false),
        id_(0),
        group_(-1),
        parent_(NULL),
        visible_(true),
        enabled_(true),
        notify_enter_exit_on_child_(false),
        registered_for_visible_bounds_notification_(false),
        needs_layout_(true),
        snap_layer_to_pixel_boundary_(false),
        flip_canvas_on_paint_for_rtl_ui_(false),
        paint_to_layer_(false),
        accelerator_focus_manager_(NULL),
        registered_accelerator_count_(0),
        next_focusable_view_(NULL),
        previous_focusable_view_(NULL),
        focus_behavior_(FocusBehavior::NEVER),
        context_menu_controller_(NULL),
        drag_controller_(NULL),
        native_view_accessibility_(NULL) {
    SetTargetHandler(this);
  }
  
  View::~View() {
    if (parent_)
      parent_->RemoveChildView(this);
  
    ViewStorage::GetInstance()->ViewRemoved(this);
  
    for (Views::const_iterator i(children_.begin()); i != children_.end(); ++i) {
      (*i)->parent_ = NULL;
      if (!(*i)->owned_by_client_)
        delete *i;
    }
  
    // Release ownership of the native accessibility object, but it's
    // reference-counted on some platforms, so it may not be deleted right away.
    if (native_view_accessibility_)
      native_view_accessibility_->Destroy();
  }
  
  // Tree operations -------------------------------------------------------------
  
  const Widget* View::GetWidget() const {
    // The root view holds a reference to this view hierarchy's Widget.
    return parent_ ? parent_->GetWidget() : NULL;
  }
  
  Widget* View::GetWidget() {
    return const_cast<Widget*>(const_cast<const View*>(this)->GetWidget());
  }
  
  void View::AddChildView(View* view) {
    if (view->parent_ == this)
      return;
    AddChildViewAt(view, child_count());
  }
  
  void View::AddChildViewAt(View* view, int index) {
    CHECK_NE(view, this) << "You cannot add a view as its own child";
    DCHECK_GE(index, 0);
    DCHECK_LE(index, child_count());
  
    // If |view| has a parent, remove it from its parent.
    View* parent = view->parent_;
    ui::NativeTheme* old_theme = NULL;
    if (parent) {
      old_theme = view->GetNativeTheme();
      if (parent == this) {
        ReorderChildView(view, index);
        return;
      }
      parent->DoRemoveChildView(view, true, true, false, this);
    }
  
    // Sets the prev/next focus views.
    InitFocusSiblings(view, index);
  
    view->parent_ = this;
    children_.insert(children_.begin() + index, view);
  
    // Ensure the layer tree matches the view tree before calling to any client
    // code. This way if client code further modifies the view tree we are in a
    // sane state.
    const bool did_reparent_any_layers = view->UpdateParentLayers();
    Widget* widget = GetWidget();
    if (did_reparent_any_layers && widget)
      widget->UpdateRootLayers();
  
    ReorderLayers();
  
    // Make sure the visibility of the child layers are correct.
    // If any of the parent View is hidden, then the layers of the subtree
    // rooted at |this| should be hidden. Otherwise, all the child layers should
    // inherit the visibility of the owner View.
    view->UpdateLayerVisibility();
  
    if (widget) {
      const ui::NativeTheme* new_theme = view->GetNativeTheme();
      if (new_theme != old_theme)
        view->PropagateNativeThemeChanged(new_theme);
    }
  
    ViewHierarchyChangedDetails details(true, this, view, parent);
  
    for (View* v = this; v; v = v->parent_)
      v->ViewHierarchyChangedImpl(false, details);
  
    view->PropagateAddNotifications(details);
  
    UpdateTooltip();
  
    if (widget) {
      RegisterChildrenForVisibleBoundsNotification(view);
  
      if (view->visible())
        view->SchedulePaint();
    }
  
    if (layout_manager_.get())
      layout_manager_->ViewAdded(this, view);
  }
  
  void View::ReorderChildView(View* view, int index) {
    DCHECK_EQ(view->parent_, this);
    if (index < 0)
      index = child_count() - 1;
    else if (index >= child_count())
      return;
    if (children_[index] == view)
      return;
  
    const Views::iterator i(std::find(children_.begin(), children_.end(), view));
    DCHECK(i != children_.end());
    children_.erase(i);
  
    // Unlink the view first
    View* next_focusable = view->next_focusable_view_;
    View* prev_focusable = view->previous_focusable_view_;
    if (prev_focusable)
      prev_focusable->next_focusable_view_ = next_focusable;
    if (next_focusable)
      next_focusable->previous_focusable_view_ = prev_focusable;
  
    // Add it in the specified index now.
    InitFocusSiblings(view, index);
    children_.insert(children_.begin() + index, view);
  
    ReorderLayers();
  }
  
  void View::RemoveChildView(View* view) {
    DoRemoveChildView(view, true, true, false, NULL);
  }
  
  void View::RemoveAllChildViews(bool delete_children) {
    while (!children_.empty())
      DoRemoveChildView(children_.front(), false, false, delete_children, NULL);
    UpdateTooltip();
  }
  
  bool View::Contains(const View* view) const {
    for (const View* v = view; v; v = v->parent_) {
      if (v == this)
        return true;
    }
    return false;
  }
  
  int View::GetIndexOf(const View* view) const {
    Views::const_iterator i(std::find(children_.begin(), children_.end(), view));
    return i != children_.end() ? static_cast<int>(i - children_.begin()) : -1;
  }
  
  // Size and disposition --------------------------------------------------------
  
  void View::SetBounds(int x, int y, int width, int height) {
    SetBoundsRect(gfx::Rect(x, y, std::max(0, width), std::max(0, height)));
  }
  
  void View::SetBoundsRect(const gfx::Rect& bounds) {
    if (bounds == bounds_) {
      if (needs_layout_) {
        needs_layout_ = false;
        Layout();
      }
      return;
    }
  
    if (visible_) {
      // Paint where the view is currently.
      SchedulePaintBoundsChanged(
          bounds_.size() == bounds.size() ? SCHEDULE_PAINT_SIZE_SAME :
          SCHEDULE_PAINT_SIZE_CHANGED);
    }
  
    gfx::Rect prev = bounds_;
    bounds_ = bounds;
    BoundsChanged(prev);
  }
  
  void View::SetSize(const gfx::Size& size) {
    SetBounds(x(), y(), size.width(), size.height());
  }
  
  void View::SetPosition(const gfx::Point& position) {
    SetBounds(position.x(), position.y(), width(), height());
  }
  
  void View::SetX(int x) {
    SetBounds(x, y(), width(), height());
  }
  
  void View::SetY(int y) {
    SetBounds(x(), y, width(), height());
  }
  
  gfx::Rect View::GetContentsBounds() const {
    gfx::Rect contents_bounds(GetLocalBounds());
    if (border_.get())
      contents_bounds.Inset(border_->GetInsets());
    return contents_bounds;
  }
  
  gfx::Rect View::GetLocalBounds() const {
    return gfx::Rect(size());
  }
  
  gfx::Insets View::GetInsets() const {
    return border_.get() ? border_->GetInsets() : gfx::Insets();
  }
  
  gfx::Rect View::GetVisibleBounds() const {
    if (!IsDrawn())
      return gfx::Rect();
    gfx::Rect vis_bounds(GetLocalBounds());
    gfx::Rect ancestor_bounds;
    const View* view = this;
    gfx::Transform transform;
  
    while (view != NULL && !vis_bounds.IsEmpty()) {
      transform.ConcatTransform(view->GetTransform());
      gfx::Transform translation;
      translation.Translate(static_cast<float>(view->GetMirroredX()),
                            static_cast<float>(view->y()));
      transform.ConcatTransform(translation);
  
      vis_bounds = view->ConvertRectToParent(vis_bounds);
      const View* ancestor = view->parent_;
      if (ancestor != NULL) {
        ancestor_bounds.SetRect(0, 0, ancestor->width(), ancestor->height());
        vis_bounds.Intersect(ancestor_bounds);
      } else if (!view->GetWidget()) {
        // If the view has no Widget, we're not visible. Return an empty rect.
        return gfx::Rect();
      }
      view = ancestor;
    }
    if (vis_bounds.IsEmpty())
      return vis_bounds;
    // Convert back to this views coordinate system.
    gfx::RectF views_vis_bounds(vis_bounds);
    transform.TransformRectReverse(&views_vis_bounds);
    // Partially visible pixels should be considered visible.
    return gfx::ToEnclosingRect(views_vis_bounds);
  }
  
  gfx::Rect View::GetBoundsInScreen() const {
    gfx::Point origin;
    View::ConvertPointToScreen(this, &origin);
    return gfx::Rect(origin, size());
  }
  
  gfx::Size View::GetPreferredSize() const {
    if (layout_manager_.get())
      return layout_manager_->GetPreferredSize(this);
    return gfx::Size();
  }
  
  int View::GetBaseline() const {
    return -1;
  }
  
  void View::SizeToPreferredSize() {
    gfx::Size prefsize = GetPreferredSize();
    if ((prefsize.width() != width()) || (prefsize.height() != height()))
      SetBounds(x(), y(), prefsize.width(), prefsize.height());
  }
  
  gfx::Size View::GetMinimumSize() const {
    return GetPreferredSize();
  }
  
  gfx::Size View::GetMaximumSize() const {
    return gfx::Size();
  }
  
  int View::GetHeightForWidth(int w) const {
    if (layout_manager_.get())
      return layout_manager_->GetPreferredHeightForWidth(this, w);
    return GetPreferredSize().height();
  }
  
  void View::SetVisible(bool visible) {
    if (visible != visible_) {
      // If the View is currently visible, schedule paint to refresh parent.
      // TODO(beng): not sure we should be doing this if we have a layer.
      if (visible_)
        SchedulePaint();
  
      visible_ = visible;
      AdvanceFocusIfNecessary();
  
      // Notify the parent.
      if (parent_) {
        parent_->ChildVisibilityChanged(this);
        parent_->NotifyAccessibilityEvent(ui::AX_EVENT_CHILDREN_CHANGED, false);
      }
  
      // This notifies all sub-views recursively.
      PropagateVisibilityNotifications(this, visible_);
      UpdateLayerVisibility();
  
      // If we are newly visible, schedule paint.
      if (visible_)
        SchedulePaint();
    }
  }
  
  bool View::IsDrawn() const {
    return visible_ && parent_ ? parent_->IsDrawn() : false;
  }
  
  void View::SetEnabled(bool enabled) {
    if (enabled != enabled_) {
      enabled_ = enabled;
      AdvanceFocusIfNecessary();
      OnEnabledChanged();
    }
  }
  
  void View::OnEnabledChanged() {
    SchedulePaint();
  }
  
  // Transformations -------------------------------------------------------------
  
  gfx::Transform View::GetTransform() const {
    return layer() ? layer()->transform() : gfx::Transform();
  }
  
  void View::SetTransform(const gfx::Transform& transform) {
    if (transform.IsIdentity()) {
      if (layer()) {
        layer()->SetTransform(transform);
        if (!paint_to_layer_)
          DestroyLayer();
      } else {
        // Nothing.
      }
    } else {
      if (!layer())
        CreateLayer();
      layer()->SetTransform(transform);
      layer()->ScheduleDraw();
    }
  }
  
  void View::SetPaintToLayer(bool paint_to_layer) {
    if (paint_to_layer_ == paint_to_layer)
      return;
  
    paint_to_layer_ = paint_to_layer;
    if (paint_to_layer_ && !layer()) {
      CreateLayer();
    } else if (!paint_to_layer_ && layer()) {
      DestroyLayer();
    }
  }
  
  std::unique_ptr<ui::Layer> View::RecreateLayer() {
    std::unique_ptr<ui::Layer> old_layer = LayerOwner::RecreateLayer();
    Widget* widget = GetWidget();
    if (widget)
      widget->UpdateRootLayers();
    return old_layer;
  }
  
  // RTL positioning -------------------------------------------------------------
  
  gfx::Rect View::GetMirroredBounds() const {
    gfx::Rect bounds(bounds_);
    bounds.set_x(GetMirroredX());
    return bounds;
  }
  
  gfx::Point View::GetMirroredPosition() const {
    return gfx::Point(GetMirroredX(), y());
  }
  
  int View::GetMirroredX() const {
    return parent_ ? parent_->GetMirroredXForRect(bounds_) : x();
  }
  
  int View::GetMirroredXForRect(const gfx::Rect& bounds) const {
    return base::i18n::IsRTL() ?
        (width() - bounds.x() - bounds.width()) : bounds.x();
  }
  
  int View::GetMirroredXInView(int x) const {
    return base::i18n::IsRTL() ? width() - x : x;
  }
  
  int View::GetMirroredXWithWidthInView(int x, int w) const {
    return base::i18n::IsRTL() ? width() - x - w : x;
  }
  
  // Layout ----------------------------------------------------------------------
  
  void View::Layout() {
    needs_layout_ = false;
  
    // If we have a layout manager, let it handle the layout for us.
    if (layout_manager_.get())
      layout_manager_->Layout(this);
  
    // Make sure to propagate the Layout() call to any children that haven't
    // received it yet through the layout manager and need to be laid out. This
    // is needed for the case when the child requires a layout but its bounds
    // weren't changed by the layout manager. If there is no layout manager, we
    // just propagate the Layout() call down the hierarchy, so whoever receives
    // the call can take appropriate action.
    for (int i = 0, count = child_count(); i < count; ++i) {
      View* child = child_at(i);
      if (child->needs_layout_ || !layout_manager_.get()) {
        TRACE_EVENT1("views", "View::Layout", "class", child->GetClassName());
        child->needs_layout_ = false;
        child->Layout();
      }
    }
  }
  
  void View::InvalidateLayout() {
    // Always invalidate up. This is needed to handle the case of us already being
    // valid, but not our parent.
    needs_layout_ = true;
    if (parent_)
      parent_->InvalidateLayout();
  }
  
  LayoutManager* View::GetLayoutManager() const {
    return layout_manager_.get();
  }
  
  void View::SetLayoutManager(LayoutManager* layout_manager) {
    if (layout_manager_.get())
      layout_manager_->Uninstalled(this);
  
    layout_manager_.reset(layout_manager);
    if (layout_manager_.get())
      layout_manager_->Installed(this);
  }
  
  void View::SnapLayerToPixelBoundary() {
    if (!layer())
      return;
  
    if (snap_layer_to_pixel_boundary_ && layer()->parent() &&
        layer()->GetCompositor()) {
      ui::SnapLayerToPhysicalPixelBoundary(layer()->parent(), layer());
    } else {
      // Reset the offset.
      layer()->SetSubpixelPositionOffset(gfx::Vector2dF());
    }
  }
  
  // Attributes ------------------------------------------------------------------
  
  const char* View::GetClassName() const {
    return kViewClassName;
  }
  
  const View* View::GetAncestorWithClassName(const std::string& name) const {
    for (const View* view = this; view; view = view->parent_) {
      if (!strcmp(view->GetClassName(), name.c_str()))
        return view;
    }
    return NULL;
  }
  
  View* View::GetAncestorWithClassName(const std::string& name) {
    return const_cast<View*>(const_cast<const View*>(this)->
        GetAncestorWithClassName(name));
  }
  
  const View* View::GetViewByID(int id) const {
    if (id == id_)
      return const_cast<View*>(this);
  
    for (int i = 0, count = child_count(); i < count; ++i) {
      const View* view = child_at(i)->GetViewByID(id);
      if (view)
        return view;
    }
    return NULL;
  }
  
  View* View::GetViewByID(int id) {
    return const_cast<View*>(const_cast<const View*>(this)->GetViewByID(id));
  }
  
  void View::SetGroup(int gid) {
    // Don't change the group id once it's set.
    DCHECK(group_ == -1 || group_ == gid);
    group_ = gid;
  }
  
  int View::GetGroup() const {
    return group_;
  }
  
  bool View::IsGroupFocusTraversable() const {
    return true;
  }
  
  void View::GetViewsInGroup(int group, Views* views) {
    if (group_ == group)
      views->push_back(this);
  
    for (int i = 0, count = child_count(); i < count; ++i)
      child_at(i)->GetViewsInGroup(group, views);
  }
  
  View* View::GetSelectedViewForGroup(int group) {
    Views views;
    GetWidget()->GetRootView()->GetViewsInGroup(group, &views);
    return views.empty() ? NULL : views[0];
  }
  
  // Coordinate conversion -------------------------------------------------------
  
  // static
  void View::ConvertPointToTarget(const View* source,
                                  const View* target,
                                  gfx::Point* point) {
    DCHECK(source);
    DCHECK(target);
    if (source == target)
      return;
  
    const View* root = GetHierarchyRoot(target);
    CHECK_EQ(GetHierarchyRoot(source), root);
  
    if (source != root)
      source->ConvertPointForAncestor(root, point);
  
    if (target != root)
      target->ConvertPointFromAncestor(root, point);
  }
  
  // static
  void View::ConvertRectToTarget(const View* source,
                                 const View* target,
                                 gfx::RectF* rect) {
    DCHECK(source);
    DCHECK(target);
    if (source == target)
      return;
  
    const View* root = GetHierarchyRoot(target);
    CHECK_EQ(GetHierarchyRoot(source), root);
  
    if (source != root)
      source->ConvertRectForAncestor(root, rect);
  
    if (target != root)
      target->ConvertRectFromAncestor(root, rect);
  }
  
  // static
  void View::ConvertPointToWidget(const View* src, gfx::Point* p) {
    DCHECK(src);
    DCHECK(p);
  
    src->ConvertPointForAncestor(NULL, p);
  }
  
  // static
  void View::ConvertPointFromWidget(const View* dest, gfx::Point* p) {
    DCHECK(dest);
    DCHECK(p);
  
    dest->ConvertPointFromAncestor(NULL, p);
  }
  
  // static
  void View::ConvertPointToScreen(const View* src, gfx::Point* p) {
    DCHECK(src);
    DCHECK(p);
  
    // If the view is not connected to a tree, there's nothing we can do.
    const Widget* widget = src->GetWidget();
    if (widget) {
      ConvertPointToWidget(src, p);
      *p += widget->GetClientAreaBoundsInScreen().OffsetFromOrigin();
    }
  }
  
  // static
  void View::ConvertPointFromScreen(const View* dst, gfx::Point* p) {
    DCHECK(dst);
    DCHECK(p);
  
    const views::Widget* widget = dst->GetWidget();
    if (!widget)
      return;
    *p -= widget->GetClientAreaBoundsInScreen().OffsetFromOrigin();
    ConvertPointFromWidget(dst, p);
  }
  
  gfx::Rect View::ConvertRectToParent(const gfx::Rect& rect) const {
    gfx::RectF x_rect = gfx::RectF(rect);
    GetTransform().TransformRect(&x_rect);
    x_rect.Offset(GetMirroredPosition().OffsetFromOrigin());
    // Pixels we partially occupy in the parent should be included.
    return gfx::ToEnclosingRect(x_rect);
  }
  
  gfx::Rect View::ConvertRectToWidget(const gfx::Rect& rect) const {
    gfx::Rect x_rect = rect;
    for (const View* v = this; v; v = v->parent_)
      x_rect = v->ConvertRectToParent(x_rect);
    return x_rect;
  }
  
  // Painting --------------------------------------------------------------------
  
  void View::SchedulePaint() {
    SchedulePaintInRect(GetLocalBounds());
  }
  
  void View::SchedulePaintInRect(const gfx::Rect& rect) {
    if (!visible_)
      return;
  
    if (layer()) {
      layer()->SchedulePaint(rect);
    } else if (parent_) {
      // Translate the requested paint rect to the parent's coordinate system
      // then pass this notification up to the parent.
      parent_->SchedulePaintInRect(ConvertRectToParent(rect));
    }
  }
  
  void View::Paint(const ui::PaintContext& parent_context) {
    if (!visible_)
      return;
    if (size().IsEmpty())
      return;
  
    gfx::Vector2d offset_to_parent;
    if (!layer()) {
      // If the View has a layer() then it is a paint root. Otherwise, we need to
      // add the offset from the parent into the total offset from the paint root.
      DCHECK(parent() || bounds().origin() == gfx::Point());
      offset_to_parent = GetMirroredPosition().OffsetFromOrigin();
    }
    ui::PaintContext context(parent_context, offset_to_parent);
  
    bool is_invalidated = true;
    if (context.CanCheckInvalid()) {
  #if DCHECK_IS_ON()
      gfx::Vector2d offset;
      context.Visited(this);
      View* view = this;
      while (view->parent() && !view->layer()) {
        DCHECK(view->GetTransform().IsIdentity());
        offset += view->GetMirroredPosition().OffsetFromOrigin();
        view = view->parent();
      }
      // The offset in the PaintContext should be the offset up to the paint root,
      // which we compute and verify here.
      DCHECK_EQ(context.PaintOffset().x(), offset.x());
      DCHECK_EQ(context.PaintOffset().y(), offset.y());
      // The above loop will stop when |view| is the paint root, which should be
      // the root of the current paint walk, as verified by storing the root in
      // the PaintContext.
      DCHECK_EQ(context.RootVisited(), view);
  #endif
  
      // If the View wasn't invalidated, don't waste time painting it, the output
      // would be culled.
      is_invalidated = context.IsRectInvalid(GetLocalBounds());
    }
  
    TRACE_EVENT1("views", "View::Paint", "class", GetClassName());
  
    // If the view is backed by a layer, it should paint with itself as the origin
    // rather than relative to its parent.
    bool paint_relative_to_parent = !layer();
  
    // TODO(danakj): Rework clip and transform recorder usage here to use
    // std::optional once we can do so.
    ui::ClipRecorder clip_recorder(parent_context);
    if (paint_relative_to_parent) {
      // Set the clip rect to the bounds of this View, or |clip_path_| if it's
      // been set. Note that the X (or left) position we pass to ClipRect takes
      // into consideration whether or not the View uses a right-to-left layout so
      // that we paint the View in its mirrored position if need be.
      if (clip_path_.isEmpty()) {
        clip_recorder.ClipRect(GetMirroredBounds());
      } else {
        gfx::Path clip_path_in_parent = clip_path_;
        clip_path_in_parent.offset(GetMirroredX(), y());
        clip_recorder.ClipPathWithAntiAliasing(clip_path_in_parent);
      }
    }
  
    ui::TransformRecorder transform_recorder(context);
    if (paint_relative_to_parent) {
      // Translate the graphics such that 0,0 corresponds to where
      // this View is located relative to its parent.
      gfx::Transform transform_from_parent;
      gfx::Vector2d offset_from_parent = GetMirroredPosition().OffsetFromOrigin();
      transform_from_parent.Translate(offset_from_parent.x(),
                                      offset_from_parent.y());
      transform_from_parent.PreconcatTransform(GetTransform());
      transform_recorder.Transform(transform_from_parent, size());
    }
  
    // Note that the cache is not aware of the offset of the view
    // relative to the parent since painting is always done relative to
    // the top left of the individual view.
    if (is_invalidated || !paint_cache_.UseCache(context, size())) {
      ui::PaintRecorder recorder(context, size(), &paint_cache_);
      gfx::Canvas* canvas = recorder.canvas();
  
      // If the View we are about to paint requested the canvas to be flipped, we
      // should change the transform appropriately.
      // The canvas mirroring is undone once the View is done painting so that we
      // don't pass the canvas with the mirrored transform to Views that didn't
      // request the canvas to be flipped.
      if (FlipCanvasOnPaintForRTLUI()) {
        canvas->Translate(gfx::Vector2d(width(), 0));
        canvas->Scale(-1, 1);
      }
  
      // Delegate painting the contents of the View to the virtual OnPaint method.
      OnPaint(canvas);
    }
  
    // View::Paint() recursion over the subtree.
    PaintChildren(context);
  }
  
  void View::set_background(Background* b) {
    background_.reset(b);
  }
  
  void View::SetBorder(std::unique_ptr<Border> b) {
    border_ = std::move(b);
  }
  
  const ui::ThemeProvider* View::GetThemeProvider() const {
    const Widget* widget = GetWidget();
    return widget ? widget->GetThemeProvider() : nullptr;
  }
  
  const ui::NativeTheme* View::GetNativeTheme() const {
    const Widget* widget = GetWidget();
    if (widget)
      return widget->GetNativeTheme();
  
  #if defined(OS_WIN)
    // On Windows, ui::NativeTheme::GetInstanceForWeb() returns NativeThemeWinAura
    // because that's what the renderer wants, but Views should default to
    // NativeThemeWin. TODO(estade): clean this up, see http://crbug.com/558029
    return ui::NativeThemeWin::instance();
  #else
    return ui::NativeTheme::GetInstanceForWeb();
  #endif
  }
  
  // RTL painting ----------------------------------------------------------------
  
  void View::EnableCanvasFlippingForRTLUI(bool enable) {
    flip_canvas_on_paint_for_rtl_ui_ = enable;
  }
  
  // Input -----------------------------------------------------------------------
  
  View* View::GetEventHandlerForPoint(const gfx::Point& point) {
    return GetEventHandlerForRect(gfx::Rect(point, gfx::Size(1, 1)));
  }
  
  View* View::GetEventHandlerForRect(const gfx::Rect& rect) {
    return GetEffectiveViewTargeter()->TargetForRect(this, rect);
  }
  
  bool View::CanProcessEventsWithinSubtree() const {
    return true;
  }
  
  View* View::GetTooltipHandlerForPoint(const gfx::Point& point) {
    // TODO(tdanderson): Move this implementation into ViewTargetDelegate.
    if (!HitTestPoint(point) || !CanProcessEventsWithinSubtree())
      return NULL;
  
    // Walk the child Views recursively looking for the View that most
    // tightly encloses the specified point.
    for (int i = child_count() - 1; i >= 0; --i) {
      View* child = child_at(i);
      if (!child->visible())
        continue;
  
      gfx::Point point_in_child_coords(point);
      ConvertPointToTarget(this, child, &point_in_child_coords);
      View* handler = child->GetTooltipHandlerForPoint(point_in_child_coords);
      if (handler)
        return handler;
    }
    return this;
  }
  
  gfx::NativeCursor View::GetCursor(const ui::MouseEvent& event) {
  #if defined(OS_WIN)
    static ui::Cursor arrow;
    if (!arrow.platform())
      arrow.SetPlatformCursor(LoadCursor(NULL, IDC_ARROW));
    return arrow;
  #else
    return gfx::kNullCursor;
  #endif
  }
  
  bool View::HitTestPoint(const gfx::Point& point) const {
    return HitTestRect(gfx::Rect(point, gfx::Size(1, 1)));
  }
  
  bool View::HitTestRect(const gfx::Rect& rect) const {
    return GetEffectiveViewTargeter()->DoesIntersectRect(this, rect);
  }
  
  bool View::IsMouseHovered() const {
    // If we haven't yet been placed in an onscreen view hierarchy, we can't be
    // hovered.
    if (!GetWidget())
      return false;
  
    // If mouse events are disabled, then the mouse cursor is invisible and
    // is therefore not hovering over this button.
    if (!GetWidget()->IsMouseEventsEnabled())
      return false;
  
    gfx::Point cursor_pos(display::Screen::GetScreen()->GetCursorScreenPoint());
    ConvertPointFromScreen(this, &cursor_pos);
    return HitTestPoint(cursor_pos);
  }
  
  bool View::OnMousePressed(const ui::MouseEvent& event) {
    return false;
  }
  
  bool View::OnMouseDragged(const ui::MouseEvent& event) {
    return false;
  }
  
  void View::OnMouseReleased(const ui::MouseEvent& event) {
  }
  
  void View::OnMouseCaptureLost() {
  }
  
  void View::OnMouseMoved(const ui::MouseEvent& event) {
  }
  
  void View::OnMouseEntered(const ui::MouseEvent& event) {
  }
  
  void View::OnMouseExited(const ui::MouseEvent& event) {
  }
  
  void View::SetMouseHandler(View* new_mouse_handler) {
    // |new_mouse_handler| may be NULL.
    if (parent_)
      parent_->SetMouseHandler(new_mouse_handler);
  }
  
  bool View::OnKeyPressed(const ui::KeyEvent& event) {
    return false;
  }
  
  bool View::OnKeyReleased(const ui::KeyEvent& event) {
    return false;
  }
  
  bool View::OnMouseWheel(const ui::MouseWheelEvent& event) {
    return false;
  }
  
  void View::OnKeyEvent(ui::KeyEvent* event) {
    bool consumed = (event->type() == ui::ET_KEY_PRESSED) ? OnKeyPressed(*event) :
                                                            OnKeyReleased(*event);
    if (consumed)
      event->StopPropagation();
  }
  
  void View::OnMouseEvent(ui::MouseEvent* event) {
    switch (event->type()) {
      case ui::ET_MOUSE_PRESSED:
        if (ProcessMousePressed(*event))
          event->SetHandled();
        return;
  
      case ui::ET_MOUSE_MOVED:
        if ((event->flags() & (ui::EF_LEFT_MOUSE_BUTTON |
                               ui::EF_RIGHT_MOUSE_BUTTON |
                               ui::EF_MIDDLE_MOUSE_BUTTON)) == 0) {
          OnMouseMoved(*event);
          return;
        }
        // FALL-THROUGH
      case ui::ET_MOUSE_DRAGGED:
        if (ProcessMouseDragged(*event))
          event->SetHandled();
        return;
  
      case ui::ET_MOUSE_RELEASED:
        ProcessMouseReleased(*event);
        return;
  
      case ui::ET_MOUSEWHEEL:
        if (OnMouseWheel(*event->AsMouseWheelEvent()))
          event->SetHandled();
        break;
  
      case ui::ET_MOUSE_ENTERED:
        if (event->flags() & ui::EF_TOUCH_ACCESSIBILITY)
          NotifyAccessibilityEvent(ui::AX_EVENT_HOVER, true);
        OnMouseEntered(*event);
        break;
  
      case ui::ET_MOUSE_EXITED:
        OnMouseExited(*event);
        break;
  
      default:
        return;
    }
  }
  
  void View::OnScrollEvent(ui::ScrollEvent* event) {
  }
  
  void View::OnTouchEvent(ui::TouchEvent* event) {
    NOTREACHED() << "Views should not receive touch events.";
  }
  
  void View::OnGestureEvent(ui::GestureEvent* event) {
  }
  
  const ui::InputMethod* View::GetInputMethod() const {
    Widget* widget = const_cast<Widget*>(GetWidget());
    return widget ? const_cast<const ui::InputMethod*>(widget->GetInputMethod())
                  : nullptr;
  }
  
  std::unique_ptr<ViewTargeter> View::SetEventTargeter(
      std::unique_ptr<ViewTargeter> targeter) {
    std::unique_ptr<ViewTargeter> old_targeter = std::move(targeter_);
    targeter_ = std::move(targeter);
    return old_targeter;
  }
  
  ViewTargeter* View::GetEffectiveViewTargeter() const {
    DCHECK(GetWidget());
    ViewTargeter* view_targeter = targeter();
    if (!view_targeter)
      view_targeter = GetWidget()->GetRootView()->targeter();
    CHECK(view_targeter);
    return view_targeter;
  }
  
  bool View::CanAcceptEvent(const ui::Event& event) {
    return IsDrawn();
  }
  
  ui::EventTarget* View::GetParentTarget() {
    return parent_;
  }
  
  std::unique_ptr<ui::EventTargetIterator> View::GetChildIterator() const {
    return base::WrapUnique(new ui::EventTargetIteratorImpl<View>(children_));
  }
  
  ui::EventTargeter* View::GetEventTargeter() {
    return targeter_.get();
  }
  
  void View::ConvertEventToTarget(ui::EventTarget* target,
                                  ui::LocatedEvent* event) {
    event->ConvertLocationToTarget(this, static_cast<View*>(target));
  }
  
  // Accelerators ----------------------------------------------------------------
  
  void View::AddAccelerator(const ui::Accelerator& accelerator) {
    if (!accelerators_.get())
      accelerators_.reset(new std::vector<ui::Accelerator>());
  
    if (!ContainsValue(*accelerators_.get(), accelerator))
      accelerators_->push_back(accelerator);
  
    RegisterPendingAccelerators();
  }
  
  void View::RemoveAccelerator(const ui::Accelerator& accelerator) {
    if (!accelerators_.get()) {
      NOTREACHED() << "Removing non-existing accelerator";
      return;
    }
  
    std::vector<ui::Accelerator>::iterator i(
        std::find(accelerators_->begin(), accelerators_->end(), accelerator));
    if (i == accelerators_->end()) {
      NOTREACHED() << "Removing non-existing accelerator";
      return;
    }
  
    size_t index = i - accelerators_->begin();
    accelerators_->erase(i);
    if (index >= registered_accelerator_count_) {
      // The accelerator is not registered to FocusManager.
      return;
    }
    --registered_accelerator_count_;
  
    // Providing we are attached to a Widget and registered with a focus manager,
    // we should de-register from that focus manager now.
    if (GetWidget() && accelerator_focus_manager_)
      accelerator_focus_manager_->UnregisterAccelerator(accelerator, this);
  }
  
  void View::ResetAccelerators() {
    if (accelerators_.get())
      UnregisterAccelerators(false);
  }
  
  bool View::AcceleratorPressed(const ui::Accelerator& accelerator) {
    return false;
  }
  
  bool View::CanHandleAccelerators() const {
    const Widget* widget = GetWidget();
    if (!enabled() || !IsDrawn() || !widget || !widget->IsVisible())
      return false;
  #if defined(USE_AURA) && !defined(OS_CHROMEOS)
    // Non-ChromeOS aura windows have an associated FocusManagerEventHandler which
    // adds currently focused view as an event PreTarget (see
    // DesktopNativeWidgetAura::InitNativeWidget). However, the focused view isn't
    // always the right view to handle accelerators: It should only handle them
    // when active. Only top level widgets can be active, so for child widgets
    // check if they are focused instead. ChromeOS also behaves different than
    // Linux when an extension popup is about to handle the accelerator.
    bool child = widget && widget->GetTopLevelWidget() != widget;
    bool focus_in_child =
        widget &&
        widget->GetRootView()->Contains(GetFocusManager()->GetFocusedView());
    if ((child && !focus_in_child) || (!child && !widget->IsActive()))
      return false;
  #endif
    return true;
  }
  
  // Focus -----------------------------------------------------------------------
  
  bool View::HasFocus() const {
    const FocusManager* focus_manager = GetFocusManager();
    return focus_manager && (focus_manager->GetFocusedView() == this);
  }
  
  View* View::GetNextFocusableView() {
    return next_focusable_view_;
  }
  
  const View* View::GetNextFocusableView() const {
    return next_focusable_view_;
  }
  
  View* View::GetPreviousFocusableView() {
    return previous_focusable_view_;
  }
  
  void View::SetNextFocusableView(View* view) {
    if (view)
      view->previous_focusable_view_ = this;
    next_focusable_view_ = view;
  }
  
  void View::SetFocusBehavior(FocusBehavior focus_behavior) {
    if (focus_behavior_ == focus_behavior)
      return;
  
    focus_behavior_ = focus_behavior;
    AdvanceFocusIfNecessary();
  }
  
  bool View::IsFocusable() const {
    return focus_behavior_ == FocusBehavior::ALWAYS && enabled_ && IsDrawn();
  }
  
  bool View::IsAccessibilityFocusable() const {
    return focus_behavior_ != FocusBehavior::NEVER && enabled_ && IsDrawn();
  }
  
  FocusManager* View::GetFocusManager() {
    Widget* widget = GetWidget();
    return widget ? widget->GetFocusManager() : NULL;
  }
  
  const FocusManager* View::GetFocusManager() const {
    const Widget* widget = GetWidget();
    return widget ? widget->GetFocusManager() : NULL;
  }
  
  void View::RequestFocus() {
    FocusManager* focus_manager = GetFocusManager();
    if (focus_manager) {
      bool focusable = focus_manager->keyboard_accessible()
                           ? IsAccessibilityFocusable()
                           : IsFocusable();
      if (focusable)
        focus_manager->SetFocusedView(this);
    }
  }
  
  bool View::SkipDefaultKeyEventProcessing(const ui::KeyEvent& event) {
    return false;
  }
  
  FocusTraversable* View::GetFocusTraversable() {
    return NULL;
  }
  
  FocusTraversable* View::GetPaneFocusTraversable() {
    return NULL;
  }
  
  // Tooltips --------------------------------------------------------------------
  
  bool View::GetTooltipText(const gfx::Point& p, base::string16* tooltip) const {
    return false;
  }
  
  bool View::GetTooltipTextOrigin(const gfx::Point& p, gfx::Point* loc) const {
    return false;
  }
  
  // Context menus ---------------------------------------------------------------
  
  void View::ShowContextMenu(const gfx::Point& p,
                             ui::MenuSourceType source_type) {
    if (!context_menu_controller_)
      return;
  
    context_menu_controller_->ShowContextMenuForView(this, p, source_type);
  }
  
  // static
  bool View::ShouldShowContextMenuOnMousePress() {
    return kContextMenuOnMousePress;
  }
  
  gfx::Point View::GetKeyboardContextMenuLocation() {
    gfx::Rect vis_bounds = GetVisibleBounds();
    gfx::Point screen_point(vis_bounds.x() + vis_bounds.width() / 2,
                            vis_bounds.y() + vis_bounds.height() / 2);
    ConvertPointToScreen(this, &screen_point);
    return screen_point;
  }
  
  // Drag and drop ---------------------------------------------------------------
  
  bool View::GetDropFormats(int* formats,
                            std::set<ui::Clipboard::FormatType>* format_types) {
    return false;
  }
  
  bool View::AreDropTypesRequired() {
    return false;
  }
  
  bool View::CanDrop(const OSExchangeData& data) {
    // TODO(sky): when I finish up migration, this should default to true.
    return false;
  }
  
  void View::OnDragEntered(const ui::DropTargetEvent& event) {
  }
  
  int View::OnDragUpdated(const ui::DropTargetEvent& event) {
    return ui::DragDropTypes::DRAG_NONE;
  }
  
  void View::OnDragExited() {
  }
  
  int View::OnPerformDrop(const ui::DropTargetEvent& event) {
    return ui::DragDropTypes::DRAG_NONE;
  }
  
  void View::OnDragDone() {
  }
  
  // static
  bool View::ExceededDragThreshold(const gfx::Vector2d& delta) {
    return (abs(delta.x()) > GetHorizontalDragThreshold() ||
            abs(delta.y()) > GetVerticalDragThreshold());
  }
  
  // Accessibility----------------------------------------------------------------
  
  gfx::NativeViewAccessible View::GetNativeViewAccessible() {
    if (!native_view_accessibility_)
      native_view_accessibility_ = NativeViewAccessibility::Create(this);
    if (native_view_accessibility_)
      return native_view_accessibility_->GetNativeObject();
    return NULL;
  }
  
  void View::NotifyAccessibilityEvent(
      ui::AXEvent event_type,
      bool send_native_event) {
    if (ViewsDelegate::GetInstance())
      ViewsDelegate::GetInstance()->NotifyAccessibilityEvent(this, event_type);
  
    if (send_native_event && GetWidget()) {
      if (!native_view_accessibility_)
        native_view_accessibility_ = NativeViewAccessibility::Create(this);
      if (native_view_accessibility_)
        native_view_accessibility_->NotifyAccessibilityEvent(event_type);
    }
  }
  
  // Scrolling -------------------------------------------------------------------
  
  void View::ScrollRectToVisible(const gfx::Rect& rect) {
    // We must take RTL UI mirroring into account when adjusting the position of
    // the region.
    if (parent_) {
      gfx::Rect scroll_rect(rect);
      scroll_rect.Offset(GetMirroredX(), y());
      parent_->ScrollRectToVisible(scroll_rect);
    }
  }
  
  int View::GetPageScrollIncrement(ScrollView* scroll_view,
                                   bool is_horizontal, bool is_positive) {
    return 0;
  }
  
  int View::GetLineScrollIncrement(ScrollView* scroll_view,
                                   bool is_horizontal, bool is_positive) {
    return 0;
  }
  
  ////////////////////////////////////////////////////////////////////////////////
  // View, protected:
  
  // Size and disposition --------------------------------------------------------
  
  void View::OnBoundsChanged(const gfx::Rect& previous_bounds) {
  }
  
  void View::PreferredSizeChanged() {
    InvalidateLayout();
    if (parent_)
      parent_->ChildPreferredSizeChanged(this);
  }
  
  bool View::GetNeedsNotificationWhenVisibleBoundsChange() const {
    return false;
  }
  
  void View::OnVisibleBoundsChanged() {
  }
  
  // Tree operations -------------------------------------------------------------
  
  void View::ViewHierarchyChanged(const ViewHierarchyChangedDetails& details) {
  }
  
  void View::VisibilityChanged(View* starting_from, bool is_visible) {
  }
  
  void View::NativeViewHierarchyChanged() {
    FocusManager* focus_manager = GetFocusManager();
    if (accelerator_focus_manager_ != focus_manager) {
      UnregisterAccelerators(true);
  
      if (focus_manager)
        RegisterPendingAccelerators();
    }
  }
  
  // Painting --------------------------------------------------------------------
  
  void View::PaintChildren(const ui::PaintContext& context) {
    TRACE_EVENT1("views", "View::PaintChildren", "class", GetClassName());
    for (int i = 0, count = child_count(); i < count; ++i)
      if (!child_at(i)->layer())
        child_at(i)->Paint(context);
  }
  
  void View::OnPaint(gfx::Canvas* canvas) {
    TRACE_EVENT1("views", "View::OnPaint", "class", GetClassName());
    OnPaintBackground(canvas);
    OnPaintBorder(canvas);
  }
  
  void View::OnPaintBackground(gfx::Canvas* canvas) {
    if (background_.get()) {
      TRACE_EVENT2("views", "View::OnPaintBackground",
                   "width", canvas->sk_canvas()->getBaseLayerSize().width(),
                   "height", canvas->sk_canvas()->getBaseLayerSize().height());
      background_->Paint(canvas, this);
    }
  }
  
  void View::OnPaintBorder(gfx::Canvas* canvas) {
    if (border_.get()) {
      TRACE_EVENT2("views", "View::OnPaintBorder",
                   "width", canvas->sk_canvas()->getBaseLayerSize().width(),
                   "height", canvas->sk_canvas()->getBaseLayerSize().height());
      border_->Paint(*this, canvas);
    }
  }
  
  // Accelerated Painting --------------------------------------------------------
  
  gfx::Vector2d View::CalculateOffsetToAncestorWithLayer(
      ui::Layer** layer_parent) {
    if (layer()) {
      if (layer_parent)
        *layer_parent = layer();
      return gfx::Vector2d();
    }
    if (!parent_)
      return gfx::Vector2d();
  
    return gfx::Vector2d(GetMirroredX(), y()) +
        parent_->CalculateOffsetToAncestorWithLayer(layer_parent);
  }
  
  void View::UpdateParentLayer() {
    if (!layer())
      return;
  
    ui::Layer* parent_layer = NULL;
    gfx::Vector2d offset(GetMirroredX(), y());
  
    if (parent_)
      offset += parent_->CalculateOffsetToAncestorWithLayer(&parent_layer);
  
    ReparentLayer(offset, parent_layer);
  }
  
  void View::MoveLayerToParent(ui::Layer* parent_layer,
                               const gfx::Point& point) {
    gfx::Point local_point(point);
    if (parent_layer != layer())
      local_point.Offset(GetMirroredX(), y());
    if (layer() && parent_layer != layer()) {
      parent_layer->Add(layer());
      SetLayerBounds(gfx::Rect(local_point.x(), local_point.y(),
                               width(), height()));
    } else {
      for (int i = 0, count = child_count(); i < count; ++i)
        child_at(i)->MoveLayerToParent(parent_layer, local_point);
    }
  }
  
  void View::UpdateLayerVisibility() {
    bool visible = visible_;
    for (const View* v = parent_; visible && v && !v->layer(); v = v->parent_)
      visible = v->visible();
  
    UpdateChildLayerVisibility(visible);
  }
  
  void View::UpdateChildLayerVisibility(bool ancestor_visible) {
    if (layer()) {
      layer()->SetVisible(ancestor_visible && visible_);
    } else {
      for (int i = 0, count = child_count(); i < count; ++i)
        child_at(i)->UpdateChildLayerVisibility(ancestor_visible && visible_);
    }
  }
  
  void View::UpdateChildLayerBounds(const gfx::Vector2d& offset) {
    if (layer()) {
      SetLayerBounds(GetLocalBounds() + offset);
    } else {
      for (int i = 0, count = child_count(); i < count; ++i) {
        View* child = child_at(i);
        child->UpdateChildLayerBounds(
            offset + gfx::Vector2d(child->GetMirroredX(), child->y()));
      }
    }
  }
  
  void View::OnPaintLayer(const ui::PaintContext& context) {
    Paint(context);
  }
  
  void View::OnDelegatedFrameDamage(
      const gfx::Rect& damage_rect_in_dip) {
  }
  
  void View::OnDeviceScaleFactorChanged(float device_scale_factor) {
    snap_layer_to_pixel_boundary_ =
        (device_scale_factor - std::floor(device_scale_factor)) != 0.0f;
    SnapLayerToPixelBoundary();
    // Repainting with new scale factor will paint the content at the right scale.
  }
  
  base::Closure View::PrepareForLayerBoundsChange() {
    return base::Closure();
  }
  
  void View::ReorderLayers() {
    View* v = this;
    while (v && !v->layer())
      v = v->parent();
  
    Widget* widget = GetWidget();
    if (!v) {
      if (widget) {
        ui::Layer* layer = widget->GetLayer();
        if (layer)
          widget->GetRootView()->ReorderChildLayers(layer);
      }
    } else {
      v->ReorderChildLayers(v->layer());
    }
  
    if (widget) {
      // Reorder the widget's child NativeViews in case a child NativeView is
      // associated with a view (eg via a NativeViewHost). Always do the
      // reordering because the associated NativeView's layer (if it has one)
      // is parented to the widget's layer regardless of whether the host view has
      // an ancestor with a layer.
      widget->ReorderNativeViews();
    }
  }
  
  void View::ReorderChildLayers(ui::Layer* parent_layer) {
    if (layer() && layer() != parent_layer) {
      DCHECK_EQ(parent_layer, layer()->parent());
      parent_layer->StackAtBottom(layer());
    } else {
      // Iterate backwards through the children so that a child with a layer
      // which is further to the back is stacked above one which is further to
      // the front.
      for (Views::reverse_iterator it(children_.rbegin());
           it != children_.rend(); ++it) {
        (*it)->ReorderChildLayers(parent_layer);
      }
    }
  }
  
  // Input -----------------------------------------------------------------------
  
  View::DragInfo* View::GetDragInfo() {
    return parent_ ? parent_->GetDragInfo() : NULL;
  }
  
  // Focus -----------------------------------------------------------------------
  
  void View::OnFocus() {
    // TODO(beng): Investigate whether it's possible for us to move this to
    //             Focus().
    // By default, we clear the native focus. This ensures that no visible native
    // view as the focus and that we still receive keyboard inputs.
    FocusManager* focus_manager = GetFocusManager();
    if (focus_manager)
      focus_manager->ClearNativeFocus();
  
    // TODO(beng): Investigate whether it's possible for us to move this to
    //             Focus().
    // Notify assistive technologies of the focus change.
    NotifyAccessibilityEvent(ui::AX_EVENT_FOCUS, true);
  }
  
  void View::OnBlur() {
  }
  
  void View::Focus() {
    OnFocus();
  }
  
  void View::Blur() {
    OnBlur();
  }
  
  // Tooltips --------------------------------------------------------------------
  
  void View::TooltipTextChanged() {
    Widget* widget = GetWidget();
    // TooltipManager may be null if there is a problem creating it.
    if (widget && widget->GetTooltipManager())
      widget->GetTooltipManager()->TooltipTextChanged(this);
  }
  
  // Drag and drop ---------------------------------------------------------------
  
  int View::GetDragOperations(const gfx::Point& press_pt) {
    return drag_controller_ ?
        drag_controller_->GetDragOperationsForView(this, press_pt) :
        ui::DragDropTypes::DRAG_NONE;
  }
  
  void View::WriteDragData(const gfx::Point& press_pt, OSExchangeData* data) {
    DCHECK(drag_controller_);
    drag_controller_->WriteDragDataForView(this, press_pt, data);
  }
  
  bool View::InDrag() const {
    const Widget* widget = GetWidget();
    return widget ? widget->dragged_view() == this : false;
  }
  
  int View::GetHorizontalDragThreshold() {
    // TODO(jennyz): This value may need to be adjusted for different platforms
    // and for different display density.
    return kDefaultHorizontalDragThreshold;
  }
  
  int View::GetVerticalDragThreshold() {
    // TODO(jennyz): This value may need to be adjusted for different platforms
    // and for different display density.
    return kDefaultVerticalDragThreshold;
  }
  
  // Debugging -------------------------------------------------------------------
  
  #if !defined(NDEBUG)
  
  std::string View::PrintViewGraph(bool first) {
    return DoPrintViewGraph(first, this);
  }
  
  std::string View::DoPrintViewGraph(bool first, View* view_with_children) {
    // 64-bit pointer = 16 bytes of hex + "0x" + '\0' = 19.
    const size_t kMaxPointerStringLength = 19;
  
    std::string result;
  
    if (first)
      result.append("digraph {\n");
  
    // Node characteristics.
    char p[kMaxPointerStringLength];
  
    const std::string class_name(GetClassName());
    size_t base_name_index = class_name.find_last_of('/');
    if (base_name_index == std::string::npos)
      base_name_index = 0;
    else
      base_name_index++;
  
    char bounds_buffer[512];
  
    // Information about current node.
    base::snprintf(p, arraysize(bounds_buffer), "%p", view_with_children);
    result.append("  N");
    result.append(p + 2);
    result.append(" [label=\"");
  
    result.append(class_name.substr(base_name_index).c_str());
  
    base::snprintf(bounds_buffer,
                   arraysize(bounds_buffer),
                   "\\n bounds: (%d, %d), (%dx%d)",
                   bounds().x(),
                   bounds().y(),
                   bounds().width(),
                   bounds().height());
    result.append(bounds_buffer);
  
    gfx::DecomposedTransform decomp;
    if (!GetTransform().IsIdentity() &&
        gfx::DecomposeTransform(&decomp, GetTransform())) {
      base::snprintf(bounds_buffer,
                     arraysize(bounds_buffer),
                     "\\n translation: (%f, %f)",
                     decomp.translate[0],
                     decomp.translate[1]);
      result.append(bounds_buffer);
  
      base::snprintf(bounds_buffer,
                     arraysize(bounds_buffer),
                     "\\n rotation: %3.2f",
                     std::acos(decomp.quaternion[3]) * 360.0 / M_PI);
      result.append(bounds_buffer);
  
      base::snprintf(bounds_buffer,
                     arraysize(bounds_buffer),
                     "\\n scale: (%2.4f, %2.4f)",
                     decomp.scale[0],
                     decomp.scale[1]);
      result.append(bounds_buffer);
    }
  
    result.append("\"");
    if (!parent_)
      result.append(", shape=box");
    if (layer()) {
      if (layer()->has_external_content())
        result.append(", color=green");
      else
        result.append(", color=red");
  
      if (layer()->fills_bounds_opaquely())
        result.append(", style=filled");
    }
    result.append("]\n");
  
    // Link to parent.
    if (parent_) {
      char pp[kMaxPointerStringLength];
  
      base::snprintf(pp, kMaxPointerStringLength, "%p", parent_);
      result.append("  N");
      result.append(pp + 2);
      result.append(" -> N");
      result.append(p + 2);
      result.append("\n");
    }
  
    // Children.
    for (int i = 0, count = view_with_children->child_count(); i < count; ++i)
      result.append(view_with_children->child_at(i)->PrintViewGraph(false));
  
    if (first)
      result.append("}\n");
  
    return result;
  }
  #endif
  
  ////////////////////////////////////////////////////////////////////////////////
  // View, private:
  
  // DropInfo --------------------------------------------------------------------
  
  void View::DragInfo::Reset() {
    possible_drag = false;
    start_pt = gfx::Point();
  }
  
  void View::DragInfo::PossibleDrag(const gfx::Point& p) {
    possible_drag = true;
    start_pt = p;
  }
  
  // Painting --------------------------------------------------------------------
  
  void View::SchedulePaintBoundsChanged(SchedulePaintType type) {
    // If we have a layer and the View's size did not change, we do not need to
    // schedule any paints since the layer will be redrawn at its new location
    // during the next Draw() cycle in the compositor.
    if (!layer() || type == SCHEDULE_PAINT_SIZE_CHANGED) {
      // Otherwise, if the size changes or we don't have a layer then we need to
      // use SchedulePaint to invalidate the area occupied by the View.
      SchedulePaint();
    } else if (parent_ && type == SCHEDULE_PAINT_SIZE_SAME) {
      // The compositor doesn't Draw() until something on screen changes, so
      // if our position changes but nothing is being animated on screen, then
      // tell the compositor to redraw the scene. We know layer() exists due to
      // the above if clause.
      layer()->ScheduleDraw();
    }
  }
  
  void View::SchedulePaintOnParent() {
    if (parent_) {
      // Translate the requested paint rect to the parent's coordinate system
      // then pass this notification up to the parent.
      parent_->SchedulePaintInRect(ConvertRectToParent(GetLocalBounds()));
    }
  }
  
  // Tree operations -------------------------------------------------------------
  
  void View::DoRemoveChildView(View* view,
                               bool update_focus_cycle,
                               bool update_tool_tip,
                               bool delete_removed_view,
                               View* new_parent) {
    DCHECK(view);
  
    const Views::iterator i(std::find(children_.begin(), children_.end(), view));
    if (i == children_.end())
      return;
  
    std::unique_ptr<View> view_to_be_deleted;
    if (update_focus_cycle) {
      View* next_focusable = view->next_focusable_view_;
      View* prev_focusable = view->previous_focusable_view_;
      if (prev_focusable)
        prev_focusable->next_focusable_view_ = next_focusable;
      if (next_focusable)
        next_focusable->previous_focusable_view_ = prev_focusable;
    }
  
    Widget* widget = GetWidget();
    if (widget) {
      UnregisterChildrenForVisibleBoundsNotification(view);
      if (view->visible())
        view->SchedulePaint();
  
      if (!new_parent || new_parent->GetWidget() != widget)
        widget->NotifyWillRemoveView(view);
    }
  
    // Make sure the layers belonging to the subtree rooted at |view| get
    // removed.
    view->OrphanLayers();
    if (widget)
      widget->UpdateRootLayers();
  
    view->PropagateRemoveNotifications(this, new_parent);
    view->parent_ = nullptr;
  
    if (delete_removed_view && !view->owned_by_client_)
      view_to_be_deleted.reset(view);
  
    children_.erase(i);
  
    if (update_tool_tip)
      UpdateTooltip();
  
    if (layout_manager_)
      layout_manager_->ViewRemoved(this, view);
  }
  
  void View::PropagateRemoveNotifications(View* old_parent, View* new_parent) {
    for (int i = 0, count = child_count(); i < count; ++i)
      child_at(i)->PropagateRemoveNotifications(old_parent, new_parent);
  
    ViewHierarchyChangedDetails details(false, old_parent, this, new_parent);
    for (View* v = this; v; v = v->parent_)
      v->ViewHierarchyChangedImpl(true, details);
  }
  
  void View::PropagateAddNotifications(
      const ViewHierarchyChangedDetails& details) {
    for (int i = 0, count = child_count(); i < count; ++i)
      child_at(i)->PropagateAddNotifications(details);
    ViewHierarchyChangedImpl(true, details);
  }
  
  void View::PropagateNativeViewHierarchyChanged() {
    for (int i = 0, count = child_count(); i < count; ++i)
      child_at(i)->PropagateNativeViewHierarchyChanged();
    NativeViewHierarchyChanged();
  }
  
  void View::ViewHierarchyChangedImpl(
      bool register_accelerators,
      const ViewHierarchyChangedDetails& details) {
    if (register_accelerators) {
      if (details.is_add) {
        // If you get this registration, you are part of a subtree that has been
        // added to the view hierarchy.
        if (GetFocusManager())
          RegisterPendingAccelerators();
      } else {
        if (details.child == this)
          UnregisterAccelerators(true);
      }
    }
  
    ViewHierarchyChanged(details);
    details.parent->needs_layout_ = true;
  }
  
  void View::PropagateNativeThemeChanged(const ui::NativeTheme* theme) {
    for (int i = 0, count = child_count(); i < count; ++i)
      child_at(i)->PropagateNativeThemeChanged(theme);
    OnNativeThemeChanged(theme);
  }
  
  // Size and disposition --------------------------------------------------------
  
  void View::PropagateVisibilityNotifications(View* start, bool is_visible) {
    for (int i = 0, count = child_count(); i < count; ++i)
      child_at(i)->PropagateVisibilityNotifications(start, is_visible);
    VisibilityChangedImpl(start, is_visible);
  }
  
  void View::VisibilityChangedImpl(View* starting_from, bool is_visible) {
    VisibilityChanged(starting_from, is_visible);
  }
  
  void View::BoundsChanged(const gfx::Rect& previous_bounds) {
    if (visible_) {
      // Paint the new bounds.
      SchedulePaintBoundsChanged(
          bounds_.size() == previous_bounds.size() ? SCHEDULE_PAINT_SIZE_SAME :
          SCHEDULE_PAINT_SIZE_CHANGED);
    }
  
    if (layer()) {
      if (parent_) {
        SetLayerBounds(GetLocalBounds() +
                       gfx::Vector2d(GetMirroredX(), y()) +
                       parent_->CalculateOffsetToAncestorWithLayer(NULL));
      } else {
        SetLayerBounds(bounds_);
      }
  
      // In RTL mode, if our width has changed, our children's mirrored bounds
      // will have changed. Update the child's layer bounds, or if it is not a
      // layer, the bounds of any layers inside the child.
      if (base::i18n::IsRTL() && bounds_.width() != previous_bounds.width()) {
        for (int i = 0; i < child_count(); ++i) {
          View* child = child_at(i);
          child->UpdateChildLayerBounds(
              gfx::Vector2d(child->GetMirroredX(), child->y()));
        }
      }
    } else {
      // If our bounds have changed, then any descendant layer bounds may have
      // changed. Update them accordingly.
      UpdateChildLayerBounds(CalculateOffsetToAncestorWithLayer(NULL));
    }
  
    OnBoundsChanged(previous_bounds);
  
    if (needs_layout_ || previous_bounds.size() != size()) {
      needs_layout_ = false;
      Layout();
    }
  
    if (GetNeedsNotificationWhenVisibleBoundsChange())
      OnVisibleBoundsChanged();
  
    // Notify interested Views that visible bounds within the root view may have
    // changed.
    if (descendants_to_notify_.get()) {
      for (Views::iterator i(descendants_to_notify_->begin());
           i != descendants_to_notify_->end(); ++i) {
        (*i)->OnVisibleBoundsChanged();
      }
    }
  }
  
  // static
  void View::RegisterChildrenForVisibleBoundsNotification(View* view) {
    if (view->GetNeedsNotificationWhenVisibleBoundsChange())
      view->RegisterForVisibleBoundsNotification();
    for (int i = 0; i < view->child_count(); ++i)
      RegisterChildrenForVisibleBoundsNotification(view->child_at(i));
  }
  
  // static
  void View::UnregisterChildrenForVisibleBoundsNotification(View* view) {
    if (view->GetNeedsNotificationWhenVisibleBoundsChange())
      view->UnregisterForVisibleBoundsNotification();
    for (int i = 0; i < view->child_count(); ++i)
      UnregisterChildrenForVisibleBoundsNotification(view->child_at(i));
  }
  
  void View::RegisterForVisibleBoundsNotification() {
    if (registered_for_visible_bounds_notification_)
      return;
  
    registered_for_visible_bounds_notification_ = true;
    for (View* ancestor = parent_; ancestor; ancestor = ancestor->parent_)
      ancestor->AddDescendantToNotify(this);
  }
  
  void View::UnregisterForVisibleBoundsNotification() {
    if (!registered_for_visible_bounds_notification_)
      return;
  
    registered_for_visible_bounds_notification_ = false;
    for (View* ancestor = parent_; ancestor; ancestor = ancestor->parent_)
      ancestor->RemoveDescendantToNotify(this);
  }
  
  void View::AddDescendantToNotify(View* view) {
    DCHECK(view);
    if (!descendants_to_notify_.get())
      descendants_to_notify_.reset(new Views);
    descendants_to_notify_->push_back(view);
  }
  
  void View::RemoveDescendantToNotify(View* view) {
    DCHECK(view && descendants_to_notify_.get());
    Views::iterator i(std::find(
        descendants_to_notify_->begin(), descendants_to_notify_->end(), view));
    DCHECK(i != descendants_to_notify_->end());
    descendants_to_notify_->erase(i);
    if (descendants_to_notify_->empty())
      descendants_to_notify_.reset();
  }
  
  void View::SetLayerBounds(const gfx::Rect& bounds) {
    layer()->SetBounds(bounds);
    SnapLayerToPixelBoundary();
  }
  
  // Transformations -------------------------------------------------------------
  
  bool View::GetTransformRelativeTo(const View* ancestor,
                                    gfx::Transform* transform) const {
    const View* p = this;
  
    while (p && p != ancestor) {
      transform->ConcatTransform(p->GetTransform());
      gfx::Transform translation;
      translation.Translate(static_cast<float>(p->GetMirroredX()),
                            static_cast<float>(p->y()));
      transform->ConcatTransform(translation);
  
      p = p->parent_;
    }
  
    return p == ancestor;
  }
  
  // Coordinate conversion -------------------------------------------------------
  
  bool View::ConvertPointForAncestor(const View* ancestor,
                                     gfx::Point* point) const {
    gfx::Transform trans;
    // TODO(sad): Have some way of caching the transformation results.
    bool result = GetTransformRelativeTo(ancestor, &trans);
    auto p = gfx::Point3F(gfx::PointF(*point));
    trans.TransformPoint(&p);
    *point = gfx::ToFlooredPoint(p.AsPointF());
    return result;
  }
  
  bool View::ConvertPointFromAncestor(const View* ancestor,
                                      gfx::Point* point) const {
    gfx::Transform trans;
    bool result = GetTransformRelativeTo(ancestor, &trans);
    auto p = gfx::Point3F(gfx::PointF(*point));
    trans.TransformPointReverse(&p);
    *point = gfx::ToFlooredPoint(p.AsPointF());
    return result;
  }
  
  bool View::ConvertRectForAncestor(const View* ancestor,
                                    gfx::RectF* rect) const {
    gfx::Transform trans;
    // TODO(sad): Have some way of caching the transformation results.
    bool result = GetTransformRelativeTo(ancestor, &trans);
    trans.TransformRect(rect);
    return result;
  }
  
  bool View::ConvertRectFromAncestor(const View* ancestor,
                                     gfx::RectF* rect) const {
    gfx::Transform trans;
    bool result = GetTransformRelativeTo(ancestor, &trans);
    trans.TransformRectReverse(rect);
    return result;
  }
  
  // Accelerated painting --------------------------------------------------------
  
  void View::CreateLayer() {
    // A new layer is being created for the view. So all the layers of the
    // sub-tree can inherit the visibility of the corresponding view.
    for (int i = 0, count = child_count(); i < count; ++i)
      child_at(i)->UpdateChildLayerVisibility(true);
  
    SetLayer(new ui::Layer());
    layer()->set_delegate(this);
    layer()->set_name(GetClassName());
  
    UpdateParentLayers();
    UpdateLayerVisibility();
  
    // The new layer needs to be ordered in the layer tree according
    // to the view tree. Children of this layer were added in order
    // in UpdateParentLayers().
    if (parent())
      parent()->ReorderLayers();
  
    Widget* widget = GetWidget();
    if (widget)
      widget->UpdateRootLayers();
  
    // Before having its own Layer, this View may have painted in to a Layer owned
    // by an ancestor View. Scheduling a paint on the parent View will erase this
    // View's painting effects on the ancestor View's Layer.
    // (See crbug.com/551492)
    SchedulePaintOnParent();
  }
  
  bool View::UpdateParentLayers() {
    // Attach all top-level un-parented layers.
    if (layer()) {
      if (!layer()->parent()) {
        UpdateParentLayer();
        return true;
      }
      // The layers of any child views are already in place, so we can stop
      // iterating here.
      return false;
    }
    bool result = false;
    for (int i = 0, count = child_count(); i < count; ++i) {
      if (child_at(i)->UpdateParentLayers())
        result = true;
    }
    return result;
  }
  
  void View::OrphanLayers() {
    if (layer()) {
      if (layer()->parent())
        layer()->parent()->Remove(layer());
  
      // The layer belonging to this View has already been orphaned. It is not
      // necessary to orphan the child layers.
      return;
    }
    for (int i = 0, count = child_count(); i < count; ++i)
      child_at(i)->OrphanLayers();
  }
  
  void View::ReparentLayer(const gfx::Vector2d& offset, ui::Layer* parent_layer) {
    layer()->SetBounds(GetLocalBounds() + offset);
    DCHECK_NE(layer(), parent_layer);
    if (parent_layer)
      parent_layer->Add(layer());
    layer()->SchedulePaint(GetLocalBounds());
    MoveLayerToParent(layer(), gfx::Point());
  }
  
  void View::DestroyLayer() {
    ui::Layer* new_parent = layer()->parent();
    std::vector<ui::Layer*> children = layer()->children();
    for (size_t i = 0; i < children.size(); ++i) {
      layer()->Remove(children[i]);
      if (new_parent)
        new_parent->Add(children[i]);
    }
  
    LayerOwner::DestroyLayer();
  
    if (new_parent)
      ReorderLayers();
  
    UpdateChildLayerBounds(CalculateOffsetToAncestorWithLayer(NULL));
  
    SchedulePaint();
  
    Widget* widget = GetWidget();
    if (widget)
      widget->UpdateRootLayers();
  }
  
  // Input -----------------------------------------------------------------------
  
  bool View::ProcessMousePressed(const ui::MouseEvent& event) {
    int drag_operations =
        (enabled_ && event.IsOnlyLeftMouseButton() &&
         HitTestPoint(event.location())) ?
         GetDragOperations(event.location()) : 0;
    ContextMenuController* context_menu_controller = event.IsRightMouseButton() ?
        context_menu_controller_ : 0;
    View::DragInfo* drag_info = GetDragInfo();
  
    // TODO(sky): for debugging 360238.
    int storage_id = 0;
    if (event.IsOnlyRightMouseButton() && context_menu_controller &&
        kContextMenuOnMousePress && HitTestPoint(event.location())) {
      ViewStorage* view_storage = ViewStorage::GetInstance();
      storage_id = view_storage->CreateStorageID();
      view_storage->StoreView(storage_id, this);
    }
  
    const bool enabled = enabled_;
    const bool result = OnMousePressed(event);
  
    if (!enabled)
      return result;
  
    if (event.IsOnlyRightMouseButton() && context_menu_controller &&
        kContextMenuOnMousePress) {
      // Assume that if there is a context menu controller we won't be deleted
      // from mouse pressed.
      gfx::Point location(event.location());
      if (HitTestPoint(location)) {
        if (storage_id != 0)
          CHECK_EQ(this, ViewStorage::GetInstance()->RetrieveView(storage_id));
        ConvertPointToScreen(this, &location);
        ShowContextMenu(location, ui::MENU_SOURCE_MOUSE);
        return true;
      }
    }
  
    // WARNING: we may have been deleted, don't use any View variables.
    if (drag_operations != ui::DragDropTypes::DRAG_NONE) {
      drag_info->PossibleDrag(event.location());
      return true;
    }
    return !!context_menu_controller || result;
  }
  
  bool View::ProcessMouseDragged(const ui::MouseEvent& event) {
    // Copy the field, that way if we're deleted after drag and drop no harm is
    // done.
    ContextMenuController* context_menu_controller = context_menu_controller_;
    const bool possible_drag = GetDragInfo()->possible_drag;
    if (possible_drag &&
        ExceededDragThreshold(GetDragInfo()->start_pt - event.location()) &&
        (!drag_controller_ ||
         drag_controller_->CanStartDragForView(
             this, GetDragInfo()->start_pt, event.location()))) {
      DoDrag(event, GetDragInfo()->start_pt,
             ui::DragDropTypes::DRAG_EVENT_SOURCE_MOUSE);
    } else {
      if (OnMouseDragged(event))
        return true;
      // Fall through to return value based on context menu controller.
    }
    // WARNING: we may have been deleted.
    return (context_menu_controller != NULL) || possible_drag;
  }
  
  void View::ProcessMouseReleased(const ui::MouseEvent& event) {
    if (!kContextMenuOnMousePress && context_menu_controller_ &&
        event.IsOnlyRightMouseButton()) {
      // Assume that if there is a context menu controller we won't be deleted
      // from mouse released.
      gfx::Point location(event.location());
      OnMouseReleased(event);
      if (HitTestPoint(location)) {
        ConvertPointToScreen(this, &location);
        ShowContextMenu(location, ui::MENU_SOURCE_MOUSE);
      }
    } else {
      OnMouseReleased(event);
    }
    // WARNING: we may have been deleted.
  }
  
  // Accelerators ----------------------------------------------------------------
  
  void View::RegisterPendingAccelerators() {
    if (!accelerators_.get() ||
        registered_accelerator_count_ == accelerators_->size()) {
      // No accelerators are waiting for registration.
      return;
    }
  
    if (!GetWidget()) {
      // The view is not yet attached to a widget, defer registration until then.
      return;
    }
  
    accelerator_focus_manager_ = GetFocusManager();
    if (!accelerator_focus_manager_) {
      // Some crash reports seem to show that we may get cases where we have no
      // focus manager (see bug #1291225).  This should never be the case, just
      // making sure we don't crash.
      NOTREACHED();
      return;
    }
    for (std::vector<ui::Accelerator>::const_iterator i(
             accelerators_->begin() + registered_accelerator_count_);
         i != accelerators_->end(); ++i) {
      accelerator_focus_manager_->RegisterAccelerator(
          *i, ui::AcceleratorManager::kNormalPriority, this);
    }
    registered_accelerator_count_ = accelerators_->size();
  }
  
  void View::UnregisterAccelerators(bool leave_data_intact) {
    if (!accelerators_.get())
      return;
  
    if (GetWidget()) {
      if (accelerator_focus_manager_) {
        accelerator_focus_manager_->UnregisterAccelerators(this);
        accelerator_focus_manager_ = NULL;
      }
      if (!leave_data_intact) {
        accelerators_->clear();
        accelerators_.reset();
      }
      registered_accelerator_count_ = 0;
    }
  }
  
  // Focus -----------------------------------------------------------------------
  
  void View::InitFocusSiblings(View* v, int index) {
    int count = child_count();
  
    if (count == 0) {
      v->next_focusable_view_ = NULL;
      v->previous_focusable_view_ = NULL;
    } else {
      if (index == count) {
        // We are inserting at the end, but the end of the child list may not be
        // the last focusable element. Let's try to find an element with no next
        // focusable element to link to.
        View* last_focusable_view = NULL;
        for (Views::iterator i(children_.begin()); i != children_.end(); ++i) {
            if (!(*i)->next_focusable_view_) {
              last_focusable_view = *i;
              break;
            }
        }
        if (last_focusable_view == NULL) {
          // Hum... there is a cycle in the focus list. Let's just insert ourself
          // after the last child.
          View* prev = children_[index - 1];
          v->previous_focusable_view_ = prev;
          v->next_focusable_view_ = prev->next_focusable_view_;
          prev->next_focusable_view_->previous_focusable_view_ = v;
          prev->next_focusable_view_ = v;
        } else {
          last_focusable_view->next_focusable_view_ = v;
          v->next_focusable_view_ = NULL;
          v->previous_focusable_view_ = last_focusable_view;
        }
      } else {
        View* prev = children_[index]->GetPreviousFocusableView();
        v->previous_focusable_view_ = prev;
        v->next_focusable_view_ = children_[index];
        if (prev)
          prev->next_focusable_view_ = v;
        children_[index]->previous_focusable_view_ = v;
      }
    }
  }
  
  void View::AdvanceFocusIfNecessary() {
    // Focus should only be advanced if this is the focused view and has become
    // unfocusable. If the view is still focusable or is not focused, we can
    // return early avoiding furthur unnecessary checks. Focusability check is
    // performed first as it tends to be faster.
    if (IsAccessibilityFocusable() || !HasFocus())
      return;
  
    FocusManager* focus_manager = GetFocusManager();
    if (focus_manager)
      focus_manager->AdvanceFocusIfNecessary();
  }
  
  // System events ---------------------------------------------------------------
  
  void View::PropagateThemeChanged() {
    for (int i = child_count() - 1; i >= 0; --i)
      child_at(i)->PropagateThemeChanged();
    OnThemeChanged();
  }
  
  void View::PropagateLocaleChanged() {
    for (int i = child_count() - 1; i >= 0; --i)
      child_at(i)->PropagateLocaleChanged();
    OnLocaleChanged();
  }
  
  void View::PropagateDeviceScaleFactorChanged(float device_scale_factor) {
    for (int i = child_count() - 1; i >= 0; --i)
      child_at(i)->PropagateDeviceScaleFactorChanged(device_scale_factor);
  
    // If the view is drawing to the layer, OnDeviceScaleFactorChanged() is called
    // through LayerDelegate callback.
    if (!layer())
      OnDeviceScaleFactorChanged(device_scale_factor);
  }
  
  // Tooltips --------------------------------------------------------------------
  
  void View::UpdateTooltip() {
    Widget* widget = GetWidget();
    // TODO(beng): The TooltipManager NULL check can be removed when we
    //             consolidate Init() methods and make views_unittests Init() all
    //             Widgets that it uses.
    if (widget && widget->GetTooltipManager())
      widget->GetTooltipManager()->UpdateTooltip();
  }
  
  // Drag and drop ---------------------------------------------------------------
  
  bool View::DoDrag(const ui::LocatedEvent& event,
                    const gfx::Point& press_pt,
                    ui::DragDropTypes::DragEventSource source) {
    int drag_operations = GetDragOperations(press_pt);
    if (drag_operations == ui::DragDropTypes::DRAG_NONE)
      return false;
  
    Widget* widget = GetWidget();
    // We should only start a drag from an event, implying we have a widget.
    DCHECK(widget);
  
    // Don't attempt to start a drag while in the process of dragging. This is
    // especially important on X where we can get multiple mouse move events when
    // we start the drag.
    if (widget->dragged_view())
      return false;
  
    OSExchangeData data;
    WriteDragData(press_pt, &data);
  
    // Message the RootView to do the drag and drop. That way if we're removed
    // the RootView can detect it and avoid calling us back.
    gfx::Point widget_location(event.location());
    ConvertPointToWidget(this, &widget_location);
    widget->RunShellDrag(this, data, widget_location, drag_operations, source);
    // WARNING: we may have been deleted.
    return true;
  }
  
  }  // namespace views
  